NAME

SYNOPSIS

DESCRIPTION

tee()
duplicates up to
len
bytes of data from the pipe referred to by the file descriptor
fd_in
to the pipe referred to by the file descriptor
fd_out.
It does not consume the data that is duplicated from
fd_in;
therefore, that data can be copied by a subsequent
splice(2).

flags
is a series of modifier flags, which share the name space with
splice(2)
and
vmsplice(2):

RETURN VALUE

Upon successful completion,
tee()
returns the number of bytes that were duplicated between the input
and output.
A return value of 0 means that there was no data to transfer,
and it would not make sense to block, because there are no
writers connected to the write end of the pipe referred to by
fd_in.

On error,
tee()
returns -1 and
errno
is set to indicate the error.

ERRORS

EAGAIN

SPLICE_F_NONBLOCK
was specified in
flags,
and the operation would block.

EINVAL

fd_in
or
fd_out
does not refer to a pipe; or
fd_in
and
fd_out
refer to the same pipe.

ENOMEM

Out of memory.

VERSIONS

The
tee()
system call first appeared in Linux 2.6.17;
library support was added to glibc in version 2.5.

CONFORMING TO

This system call is Linux-specific.

NOTES

Conceptually,
tee()
copies the data between the two pipes.
In reality no real data copying takes place though:
under the covers,
tee()
assigns data in the output by merely grabbing
a reference to the input.

EXAMPLE

The example below implements a basic
tee(1)
program using the
tee()
system call.
Here is an example of its use:

SEE ALSO

COLOPHON

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